Recently, various liquid crystal compositions exhibiting high dielectricities are proposed. However, there are very few liquid compositions that are acceptable in orientation and response, and have the lower limit of the temperature range of the chiral smectic C(Sc*) phase below the room temperature.
For example, by mixing compounds A, B and C shown by the following formulas (A), (B) and (C) as proposed by Goodby, etc., a liquid crystal composition having acceptable orientation and response is obtained. (In the formulas below, (S) and (R) mean that the absolute configuration of an optical active group forming its side chain is of S type or R type.) ##STR1##
Analyzing the relationship between the transition point temperature and the formulating ratio of a liquid crystal composition consisting of these compounds A, B and C, it is recognized that the optimum temperature range representing the Sc* phase is about 13.degree. C. to 55.degree. C.
The optimum temperature range of the Sc* phase of a liquid crystal composition obtained by mixing liquid crystal compounds D and E shown by the following formulas (D) and (E) is about 20.degree. C. to 65.degree. C. ##STR2##
On the other hand, there is a proposal to mix compounds having different skeltons to extend the Sc* phase temperature range. The optimum Sc* phase temperature range of a composition obtained by the foregoing compounds A to E as taught by the proposal is about 0.degree. to 63.degree. C.
As studied above, prior art strong dielectric liquid crystal compositions did not have the Sc* phase lower limit temperature sufficiently low for a reliable practical use.